Excess Mortality during the First and Second Waves of COVID-19 Spread in Japan (December 2019-May 2020); Evidence from Municipality Level Data

Abstract

The current consensus is that the new coronavirus SARS-Cov-2 was imported in Japan from Wuhan in January 2020, and that the spread resulted in a first COVID-19 outbreak in March-April. Series of daily new counts of PCR tests positive cases indicate that it was contained at a low level of prevalence. Japanese municipality level mortality data enable a closer look at the timing and extent of the outbreak. The comparison of monthly mortality rates with the average mortality rates in the previous four years confirm that excess mortality in the 6-month period ending in late May was much lower than in high prevalence OECD countries. In Tokyo, that is the epicentre of the outbreak in Japan, deviations higher that one standard deviation are observed in December and April 2020 (high mortality), and in February and May (low mortality). Data available for 1081 Japanese municipality in 32 prefectures exhibit high mortality in January and April, and low mortality in February and May. These results suggest that virus importation from Wuhan occurred from December (or earlier), resulting in a first outbreak in December-January 2019.

Note: Funding: None to declare

Declaration of Interest: None to declare

Keywords: new coronavirus, SARS-Cov-2, virus importation

JEL Classification: I10, R10